"Denny" wrote in message
ups.com...

Well, there are dielectrics and there are . . . ummm well you get the
point...

In this case the main dielectric of my condensers is glass, probably
stannous float bath soda glass... 0.100" thick with an aluminum plate
on each side... After my fingers had found the disparate temperature
rise on an early test I did a literature search for the dielectric
constant and loss factor of glass and discovered that not all glass is
equal - or as Orwell put it, some of the animals are more equal than
the others...

Anyway, Soda glass has a loss tangent of 0.01 to 0.05 and a dielectric
constant of 6 - and Borosilicate glass (Pyrex) has a loss tangent of
0.001 to 0.002 and a dielectric constant of 4... So, it would appear
that Borosilicate glass is better as a low loss dielectric... The
trade off is that with 1/3 lower Dielectric Constant I would have to
increase my plate areas by 1/3 to maintain the same capacity... The
jury is out on this... 3.5 mc is relatively low frequency... I am not
sure how much of the heating is due to the loss factor of the glass and
how much is I2R heating from the current flowing across the plates...
I spoze I could order some custom made 8" X 10" X 0.100" Pyrex plates
and compare otherwise identical condensers... OTOH, I spoze some of
the more equal animals in my house would complain over sticks and
stones in their xmas stockings after I pay for the Pyrex...

denny / k8do

Could you use some Pyrex disk, I think I have some that are about a foot in
diameter. If I can find them they are yours for the postage.